EVALUATION OF AN ELASTOMER FOR BIOMEDICAL USE IN LOAD-BEARING APPLICATIONS .1. IN-VITRO FATIGUE TESTING

The fatigue behaviour of a medical-grade thermoplastic polyolefin (TPO ) was investigated with the objective of using TPOs for endoprosthetic al aims in dental and orthopaedic applications. For this purpose, a TP O was subjected to the combined action of shear and compression fatigu e while in contact with Hanks' solution. Cyclic loading between 150 an d 1500 kPa shear stress and a number of cycles up to 9 x 10(6) was app lied. The potential fatigue damage was assessed by in-fatigue-recordin g of the mechanical hysteresis curves and, after fatigue, by swelling tests in acetic acid solutions, dynamic mechanical thermal analysis, F ourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The combined and critical application of these t echniques allowed us to conclude that this material exhibits a very sa tisfactory fatigue behaviour under the loads investigated, making this material potentially useful for endoprostheses. Moreover, biomedical prescreening tests (according to USP Class VI) were all negative, stim ulating continued research on this type of material.